We propose a perception/action approach to calibration of targeted actions like reaching or throwing. Calibration maps units of perceptual information to units of action. This mapping is perturbed by postural change, growth, aging, fatigue, specific deficits (e.g. DCD), lenses, low vision aids and prosthetics. The knowledge to be gained from this research is essential for effective therapies for the elderly or children with DCD, or for learning to use visual aids and prosthetic limbs. We will investigate calibration by manipulating two units of visual information about distance using a telestereoscope and a periscope. One unit is binocular inter-pupillary distance for vergence and the other is monocular eye height for vertical gaze angle. Each information unit will be calibrated and perturbed by 15%. Two different actions will be tested to investigate action specificity of calibration: throwing and reaching. We will investigate five questions. First, what is calibrated? We hypothesize that the slope of a distance function is calibrated because information units are calibrated. Second, how are different visual units combined to yield a single unit that can be calibrated to action? In contrast to weighted averaging theories of cue combination, we hypothesize that temporally stable units are used to calibrate unstable units. Third, is calibration different for different actions? We hypothesize that calibration is specific to actions and does not transfer between actions because the units are different. Fourth, how does limb specific calibration interact with action specific calibration? We hypothesize that limb and action specific calibration relate hierarchically and additively. Fifth, we hypothesize that long-term calibrations are specific to actions and to maximally stable information units calibrated during practice. Finally, we proposed to investigate whether calibration is a potential solution to known deficits and clumsiness suffered by the elderly and children with DCD in performing actions like reaching. Feedback from targeted actions like reaching is used to calibrate those actions so that they can be accurate. We propose to investigate whether calibration is a potential solution to known deficits and clumsiness suffered by the elderly and children with Development Coordination Disorder or whether in fact the deficits are an inability to calibrate. The knowledge to be gained from this research is essential for formulating effective physical therapies for the elderly or children with DCD, or for learning to use visual aids and prosthetic limbs.